Dip coating apparatus with height adjustable coating tubes and method of coating

ABSTRACT

A dip coating apparatus and method of dip coating. The apparatus includes a guide surface, a bendable tube, a carriage, and a support assembly. The bendable tube redirectionally engages the guide surface intermediate the first and second longitudinal ends of the tube. The carriage is vertically repositionable and cooperatively engages the tube proximate the first longitudinal end of the tube, whereby vertical repositioning of the carriage effects a change in the vertical distance between the first and second longitudinal ends of the tube. The support assembly releasably suspends an elongate workpiece for introduction of at least a portion of the workpiece into the tube through the first longitudinal end of the coating tube as the carriage is vertically repositioned upwards towards the support assembly.

BACKGROUND OF THE INVENTION

Elongate flexible workpieces, such as guidewires and catheters, areoften coated to provide a desired property or characteristic, such asenhanced lubricity, improved biological compatibility or rustresistance. The coating is commonly applied by dipping the workpieceinto a coating solution, removing the workpiece from the coatingsolution, and curing the coating.

Typical dip coating equipment employs coating tubes to retain thecoating solution and guide the flexible workpieces as they are dippedinto the solution. The top of each coating tube is usually equipped witha funnel for facilitating introduction of a workpiece into the coatingtube. The coating tubes are commonly straight vertical tubes having alength sufficient to accommodate the longest workpiece to be coated.

While generally effective for coating elongate flexible workpieces, suchequipment is rather bulky, arduous to use as the operator mustrepeatedly reach up, often above his/her head, to mount and dismount theworkpieces, and requires substantial quantities of often expensivecoating solution to “prime” the system, resulting in considerable waste.

In an effort to overcome these drawbacks, dip coating equipment has beendesigned with spiral or helical coating tubes submerged in a commonreservoir of coating solution. One such coating apparatus is disclosedin United States Published Patent Application 20060210699.

While overcoming many of the drawbacks associated with straight-tube dipcoating equipment, it has been discovered that coiled-tube dip coatingequipment does not work well with certain types of elongate flexibleworkpieces as such workpieces are not susceptible to being pushed orthreaded along the length of a coiled coating tube, resulting inincomplete coating and/or a kinked workpiece.

Accordingly, a continuing need exists for dip coating equipment capableof consistently and efficiently coating a wide variety of elongateflexible workpieces while using minimal coating solution to prime thesystem and permitting an operator to mount and dismount workpieces at acomfortable height.

SUMMARY OF THE INVENTION

A first aspect of the invention is a dip coating apparatus having aguide surface, a bendable tube, a carriage, and a support assembly. Thebendable tube redirectionally engages the guide surface intermediate thefirst and second longitudinal ends of the tube. The carriage isvertically repositionable and cooperatively engages the tube proximatethe first longitudinal end of the tube, whereby vertical repositioningof the carriage effects a change in the vertical distance between thefirst and second longitudinal ends of the tube. The support assemblyreleasably suspends an elongate workpiece for introduction of at least aportion of the workpiece into the tube through the first longitudinalend of the coating tube as the carriage is vertically repositionedupwards towards the support assembly.

A second aspect of the invention is a dip coating apparatus having atube, a carriage and a support assembly. The carriage is verticallyrepositionable and comprises a basin defining a fluid retention cavityin fluid communication with the tube for supplying fluid to the tubewhen the carriage is moved upward, and receiving overflow fluid from thetube when the carriage is moved downward. The support assemblyreleasably suspends an elongate workpiece for introduction of at least aportion of the workpiece into the tube through the first longitudinalend of the coating tube as the carriage is vertically repositionedupwards towards the support assembly.

A third aspect of the invention is a method of dip coating an elongateworkpiece. The method includes the steps of (i) moving the firstlongitudinal end of a tube defining a lumen upwards away from the secondlongitudinal end of the tube and towards a workpiece so as to introducea length of the workpiece into the lumen and into contact with coatingsolution retained within the lumen, and (ii) moving the firstlongitudinal end of the tube downward towards the second longitudinalend of the tube and away from the partially coated workpiece until thepartially coated workpiece is removed from the lumen defined by thetube.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of one embodiment of the invention.

FIG. 2 is a front view of the workpiece support assembly portion of thedip coating apparatus shown in FIG. 1 depicting a single workpiece.

FIG. 3A is a front view of the coating tube assembly portion of the dipcoating apparatus shown in FIG. 1 in the retracted position anddepicting every other tube.

FIG. 3B is a front view of the coating tube assembly portion of the dipcoating apparatus shown in FIG. 1 in the extended position and depictingevery other tube.

FIG. 4 is a side view of the coating tube assembly portion of the dipcoating apparatus shown in FIG. 1 in the refracted position.

FIG. 5 is a top view of the carriage portion of the coating tubeassembly shown in FIG. 1.

FIG. 6 is an enlarged cross-sectional side view of the carriage shown inFIG. 4 taken along line 6-6 with the tubes removed.

FIG. 7 is a top view of the take-up spool system shown in FIG. 1 withthe tubes removed.

FIG. 8 is a schematic of the fluid flow between the carriage and aseparate reservoir.

FIG. 9 is an electrical schematic of the dip coating apparatus shown inFIG. 1.

FIG. 10A is a front view of an alternative take-up system in theretracted position with a single tube attached.

FIG. 10B is a side view of the alternative take-up system shown in FIG.10A in the extended position.

FIG. 11A is a front view of one tube filled with coating solution froman alternative coating tube assembly in the retracted position.

FIG. 11B is a front view of the alternative coating tube assembly shownin FIG. 11A in the extended position.

DETAILED DESCRIPTION OF THE INVENTION

Nomenclature

-   10 Dip Coating Apparatus-   20 Workpiece Support Assembly-   30 Coating Tube Assembly-   40 Frame-   45 Carriage Support Stanchions-   50 Tube (Collapsible)-   51 First Longitudinal End of Tube-   52 Second Longitudinal End of Tube-   59 Lumen Defined by Tube-   60 Carriage-   60 a Base-   60 b Sidewalls-   61 Coupling-   62 Funnel-   65 Drive Mechanism for Carriage-   65 b Belt-   65 m Motor-   69 Fluid Retention Cavity-   70 Take-Up Spools-   75 Drive Mechanism for Take-Up Spool-   75 b Belt-   75 m Motor-   79 Nip Point-   80 Reservoir-   90 Pump-   100 Controller-   145 Traveler Support Stanchions-   170 Traveler Board-   171 Nip Roller-   172 Pulley-   179 Nip Point-   250 Tube (Bendable)-   251 First Longitudinal End of Tube-   252 Second Longitudinal End of Tube-   259 Lumen Defined by Tube-   260 Carriage-   262 Funnel-   270 Guide-   S Coating Solution-   W Workpiece-   x Horizontal Direction-   y Transverse Direction-   z Vertical Direction-   z₁ Upward Direction-   z₂ Downward Direction    Construction

First Embodiment

Referring to FIG. 1, the dip coating apparatus 10 includes a frame 40supporting a workpiece support assembly 20 over a coating tube assembly30. The workpiece support assembly 20 includes clips (unnumbered) orother fastening mechanisms for releasably suspending elongate workpiecesW in vertical z alignment above tubes 50 or 250 in the coating tubeassembly 30.

Typical workpiece support assemblies 20 suitable for use include thoseshown and described in United States Patent Application Publications2001/0026834 and 2006/0210699.

Referring to FIGS. 1, 3A and 3B, one embodiment of the coating tubeassembly 30 includes tubes 50 attached at the first longitudinal end 51to a carriage 60 and attached at the second longitudinal end 52 to atake-up spool 70.

The tubes 50 used in the embodiment depicted in FIGS. 1, 3A, 3B, 4-7,10A and 10B are collapsible, permitting the tubes 50 to be flattened forwinding onto the take-up spools 70 and for permitting the sidewalls(unnumbered) of the tube 50 to be pinched together anywhere along thelongitudinal length of the tube 50 to seal the lumen 59 defined by thetube 50. Suitable tubes 50 include those manufactured from plastic filmhaving a thickness of up to about 20 mil.

The carriage 60 used in the embodiment depicted in FIGS. 1, 3A, 3B and4-7 and the embodiment depicted in FIGS. 10A and 10B includes a base 60a, and sidewalls 60 b defining a fluid retention cavity 69 capable ofholding a supply of coating solution S. The carriage 60 is driven by anysuitable drive mechanism 65, such as a belt 65 b and electric motor 65m, to reciprocate along a vertical stanchion 45 as between a retractedposition, shown in FIGS. 3A and 10A, and an expanded position, shown inFIGS. 3B and 10B.

As shown in FIG. 4, the first longitudinal end 51 of each tube 50 issecured to the base 60 a and placed in fluid communication with thefluid retention cavity 69 by a suitable coupling 61. A guide funnel 62extends upward z₁ from each coupling 61 for guiding a workpiece Wsuspended from the workpiece support assembly 20 into the lumen 59 ofthe corresponding tube 50. An annual gap (not shown) is preferablyprovided between each coupling 61 and guide funnel 62 for permittingfluid to flow between the fluid retention cavity 69 and the lumen 59 ofthe tube 50.

A separate reservoir 80 containing additional coating solution S may beplaced in fluid communication with the fluid retention cavity 69 viasuitable inlet/outlet orifices (not shown) in the carriage 60 and thereservoir 80, for supplying additional coating solution S to the fluidretention cavity 69 when necessary and receiving any overflow of coatingsolution S from the fluid retention cavity 69. The reservoir 80 may beentirely separate from the coating apparatus 10 connected only bysuitable hosing (not shown), may be attached to the frame 40, or evenattached to the carriage 60 for movement along the stanchion 45 inconjunction with the carriage 60. Fluid flow may be effected solely bygravity, or with the aid of a pump 90.

As shown in FIGS. 1, 3A, 3B, 4, 7, 10A and 10B, the second longitudinalend 52 of each tube 50 is secured to a slack control and tensioningsystem. One suitable slack control and tensioning system, shown in FIGS.1, 3A, 3B, 4 and 7 is a take-up spool 70. The take-up spools 70 keep thetubes 50 taut by “reeling-in” and “reeling-out” the tubes 50 as thecarriage 60 moves between the retracted and expanded positions, andneatly winding any slack in the tubes 50 around the spool 70. Thetake-up spools 70 place sufficient tension on the tubes 50 to cause thetubes 50 to collapse as they come into contact with the take-up spools70, or alternatively into contact with a nip roller (not shown), so asto create a nip point 79 at which the lumen 59 of the tube 50 is sealed.The take-up spools 70 are driven by any suitable drive mechanism 75,such as a belt 75 b and electric motor 75 m.

Another suitable slack control and tensioning system, shown in FIGS. 10Aand 10B is a traveler board 170 driven by any suitable drive mechanism(not shown), such as a belt (not shown) and electric motor (not shown),to reciprocate along a vertical stanchion 145 as between a retractedposition, shown in FIG. 10A, and an expanded position shown in FIG. 10B.The traveler board 170 keeps the tubes 50 taut by moving a distancealong the vertical stanchion 145 equal and opposite to the distancetraveled by the carriage 60 along the vertical stanchion 45. The tubes50 are guided from the carriage 60 to the travel board 170 by a niproller 171 positioned immediately underneath each corresponding coupling62, and a pulley 172. As with the take-up spools 70, the traveler board170 places sufficient tension on the tubes 50 to cause the tubes 50 tocollapse as they come into contact with the nip rollers 171 so as tocreate a nip point 179 at which the lumen 59 of the tube 50 is sealed.

In order to coordinate movement of the carriage 60 and the slack controland tensioning system, the drive mechanisms for each must be coordinatedby a suitable controller 100, such as depicted schematically in FIG. 9,to ensure that the length of tubing 50 “reeled-out” from the take-upspools 70 or the distance traveled by the traveler board 170 correspondsto the distance traveled by the carriage 60. Alternatively, the carriage60 and slack control and tensioning system can be driven by the samemotor.

Second Embodiment

Referring to FIGS. 11A and 11B, a second embodiment of the coating tubeassembly 30 includes tubes 250 attached at the first longitudinal end251 to a carriage 260, sealed at the second longitudinal end 252 andfilled with a coating solution S.

The tubes 250 used in this embodiment can be bent without collapsing soas to permit the tubes 50 to be curved back upon themselves about afairly tight turning radius of less than about 20 cm, preferably lessthan about 10 cm and most preferably less than about 5 cm, withoutcollapsing the lumen 259 of the tube 250. Suitable tubes 50 includethose manufactured from rubber or polyethylene.

The tubes 250 are directed by a guide 270 which slidably engages thetubes 250. The tubes 250 can be guided along any desired path rangingfrom a 180° bend, a 90° bend, two separate 90° bends, a spiral, a helix,etc. Generally, the path should be selected to minimize the overall sizeof the entire coating tube assembly 30 while avoiding sharp turns andproviding a straight vertical section in contact with a workpiece Wbeing coated.

As with the first embodiment, the carriage 260 is driven by any suitabledrive mechanism (not shown), such as an electric motor (not shown) and abelt (not shown), to reciprocate along a vertical stanchion (not shown)as between a lower start position, shown in FIG. 11A, and an uppercoating position, shown in FIG. 11B.

A guide funnel 262 engages the first longitudinal end 251 of each tube250 for guiding a workpiece W suspended from the workpiece supportassembly 20 into the lumen 259 of the corresponding tube 250.

Use

First Embodiment

The first embodiment of the coating apparatus 10 of the presentinvention provides consistent and efficient coating of a wide variety ofelongate flexible workpieces W while using minimal coating solution S toprime the system and permitting an operator (not shown) to mount anddismount workpieces W at a comfortable height. Use involves the steps of(i) positioning the carriage 60 into the retracted position as shown inFIG. 3A, (ii) filling the fluid retention cavity 69 of the carriage 60and the lumen 59 of each tube 50 down to the nip point 79 with coatingsolution S, (iii) clipping workpieces W onto the workpiece supportassembly 20, and (iv) activating the coating apparatus 10 to perform acoating cycle.

When the slack control and tensioning system is take-up spools 70, thecoating cycle involves (a) immersing a lowermost length of eachworkpiece W suspended from the workpiece support assembly 20 intocoating solution S contained within the lumen 59 of a vertically zaligned tube 50 by simultaneously driving the carriage 60 upwards z₁towards the workpieces W while unreeling a corresponding length oftubing 50 from the take-up spool 70, causing coating solution S to flowfrom the fluid retention cavity 69 defined by the carriage 60 into thelumen 59 of each tube 50 as the length of the lumen 59 above the nippoint 79 increases, followed by (b) withdrawing the now coated lowermostlength of each workpiece W from the corresponding tube 50 by driving thecarriage 60 downward z₂ away from the workpieces W while winding acorresponding length of tubing 50 onto the take-up spool 70, causingcoating solution S to flow from the lumen 59 of each tube 50 back intothe fluid retention cavity 69 defined by the carriage 60 as the lengthof the lumen 59 above the nip point 79 decreases.

When the slack control and tensioning system is a traveler board 170,the coating cycle involves (a) immersing a lowermost length of eachworkpiece W suspended from the workpiece support assembly 20 intocoating solution S contained within the lumen 59 of a vertically alignedtube 50 by simultaneously driving the carriage 60 upwards z₁ towards theworkpieces W while driving the traveler board 170 an equal distancedownward z₂, causing coating solution S to flow from the fluid retentioncavity 69 defined by the carriage 60 into the lumen 59 of each tube 50as the length of the lumen 59 above the nip point 179 increases,followed by (b) withdrawing the now coated lowermost length of eachworkpiece W from the corresponding tube 50 by driving the carriage 60downward z₂ away from the workpieces W while driving the traveler board170 an equal distance upward z₁, causing coating solution S to flow fromthe lumen 59 of each tube 50 back into the fluid retention cavity 69defined by the carriage 60 as the length of the lumen 59 above the nippoint 79 decreases.

Second Embodiment

The second embodiment of the coating apparatus 10 of the presentinvention also provides consistent and efficient coating of a widevariety of elongate flexible workpieces W while using minimal coatingsolution S to prime the system and permitting an operator (not shown) tomount and dismount workpieces W at a comfortable height. Use involvesthe steps of (i) positioning the carriage 260 into the upper coatingposition as shown in FIG. 10B (ii) filling the lumen 259 of each tube250 with coating solution S, (iii) repositioning the carriage 260 intothe lower start position as shown in FIG. 10A, (iv) clipping workpiecesW onto the workpiece support assembly 20, and (v) activating the coatingapparatus 10 to perform a coating cycle.

The coating cycle involves (a) immersing a lowermost length of eachworkpiece W suspended from the workpiece support assembly 20 intocoating solution S contained within the lumen 259 of a verticallyaligned tube 250 by driving the carriage 260 from the lower startposition upwards towards the workpieces W into the upper coatingposition, followed by (b) withdrawing the now coated lowermost length ofeach workpiece W from the corresponding tube 250 by driving the carriage260 downward z₂ from the upper coating position away from the workpiecesW towards the lower start position.

1. A dip coating apparatus, comprising: (a) a member providing a guidesurface, effective for engaging and redirecting a bendable object, (b) abendable tube having a first longitudinal end and a second longitudinalend, and redirectionally engaging the guide surface intermediate thefirst and second longitudinal ends, (c) a vertically repositionablecarriage cooperatively engaging the tube proximate the firstlongitudinal end of the tube whereby vertical repositioning of thecarriage effects a change in the vertical distance between the first andsecond longitudinal ends of the tube, and (d) a support assembly forreleasably suspending an elongate workpiece for introductions of atleast a portion of the workpiece into the tube through the firstlongitudinal end of the tube as the carriage is vertically repositionedupwards towards the support assembly.
 2. The apparatus of claim 1wherein (i) the bendable tube is a collapsible tube, and (ii) theapparatus further comprises a nip for sealingly pinching the tubeintermediate the first and second longitudinal ends of the tube todefine a nip point on the tube which travels along the longitudinallength of the tube as the tube is vertically repositioned by thecarriage.
 3. The apparatus of claim 2 wherein the collapsible tube isconstructed from a thin, flexible film having a thickness of less than20 mil.
 4. The apparatus of claim 2 wherein the guide member is a driventake-up spool effective for winding-up any slack in the tube andfunctioning as the nip.
 5. The apparatus of claim 2 wherein the nip isfixedly attached to a stationary frame.
 6. The apparatus of claim 1wherein (i) the second longitudinal end the tube is sealed, (ii) theguide member is at least one guide pulley, and (iii) the bendable tubeis redirected at least 135° without sealingly collapsing the tube. 7.The apparatus of claim 1 wherein (i) the second longitudinal end thetube is sealed, (ii) the guide member is at least one guide pulley, and(iii) the bendable tube is redirected between 170° and 190° withoutsealingly collapsing the tube.
 8. The apparatus of claim 2 wherein thecarriage comprises a basin defining a fluid retention cavity in fluidcommunication with the tube for supplying fluid to the tube when thecarriage is moved upwards, and receiving overflow fluid from the tubewhen the carriage is moved downwards.
 9. The apparatus of claim 8further comprising a reservoir in fluid communication with the fluidretention cavity defined by the carriage for supplying fluid to thefluid retention cavity when the carriage is moved upwards, and receivingfluid from the retention cavity when the carriage is moved downwards.10. The apparatus of claim 9 further comprising a pump for pumping fluidfrom the reservoir into the fluid retention cavity.
 11. The apparatus ofclaim 1 wherein (i) the apparatus includes a plurality of bendabletubes, each (a) having a first longitudinal end and a secondlongitudinal end, (b) redirectionally engaging the guide surfaceintermediate the first and second longitudinal ends, and (c)cooperatively engaging the carriage proximate the first longitudinal endof the tube whereby vertical repositioning of the carriage effects achange in the vertical distance between the first and secondlongitudinal ends of each tube, and (ii) the support assembly iseffective for releasably suspending a plurality of elongate workpiecesfor introduction of at least a portion of each workpiece into one of thetubes through the first longitudinal end of the tube as the carriage isvertically repositioned upwards towards the support assembly.
 12. Theapparatus of claim 11 wherein the apparatus includes a separate guidemember for each tube.
 13. A dip coating apparatus, comprising: (a) atube having a first longitudinal end and a second longitudinal end, (b)a vertically repositionable carriage comprising a basin defining a fluidretention cavity in fluid communication with the tube for supplyingfluid to the tube when the carriage is moved upward, and receivingoverflow fluid from the tube when the carriage is moved downward, thecarriage cooperatively engaging the tube proximate the firstlongitudinal end of the tube whereby vertical repositioning of thecarriage effects a change in the vertical distance between the first andsecond longitudinal ends of the tube, and (c) a support assembly forreleasably suspending an elongate workpiece for introductions of atleast a portion of the workpiece into the tube through the firstlongitudinal end of the coating tube as the carriage is verticallyrepositioned upwards towards the support assembly.
 14. The apparatus ofclaim 13 further comprising a reservoir in fluid communication with thefluid retention cavity defined by the carriage for supplying fluid tothe fluid retention cavity when the carriage is moved upwards, andreceiving fluid from the retention cavity when the carriage is moveddownwards.